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Файл:Materials processing and manufacturing technologies. Учебное пособие
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homogeneous. In order to achieve the result, the clay is mixed with
water in a pug mill, a mixing chamber with one or more revolving
shafts. Before forming, the plastic clay mass is pugged. Bricks are
generally formed by the following processes: dry-press, stiff- mud
and soft-mud.
Drying. One of the main conditions for high-quality brick
production which preventing its cracking is a careful regulation of
heat and humidity. Depending on the method of forming, wet bricks
contain from 7 to 30 percent moisture. Dryer chambers evaporate
this water before the firing process starts. Temperatures usually
range from about 38 °C to 204 °C. Different types of clay demand
different drying time. It varies between 24 to 48 hours.
Hacking. During this process, a kiln or kiln car is loaded with
brick by robots or mechanical means. The kiln size determines the
number of brick to be loaded. The bricks are placed in three
different ways: face-to-face, face-to-back and cross-set. The most
uniform color is obtained when using the first method.
Firing. The typical period of brick firing ranges between 10
and 40 hours. It depends on types of a kiln and fuel. The fuel used
for the process includes coal, natural gas, methane gas from
landfills, sawdust, or their combinations.
Cooling. As the rate of cooling has a direct effect on quality
and color of brick, this important stage in manufacturing is paid
a special attention to. After the temperature has peaked and is
maintained for an exact time, the cooling process begins. Cooling
time also varies and depends on the type of a kiln. It rarely
exceeds 10 hours for tunnel kilns. Periodic kilns require from 5
to 24 hours.
De-hacking. It is the process of unloading a kiln or kiln car
after the bricks have cooled. This job is often performed by robots.
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Bricks are sorted, graded and packaged. Then, they are placed in
a storage yard or loaded into rail cars or trucks for delivery.
Task 1. Find the English equivalents for the following words
and word combinations in the text 2 (part 2).
Сушильная камера; прочность материала в высушенном
на воздухе состоянии; жаропрочность; растрескивание кирпичей; изобретение машин для производства кирпича; добыча
и хранение сырья; подготовка сырья; формование кирпичей;
сушка кирпичей; загрузка кирпичей в обжиговую печь; обжиг
и охлаждение; разгрузка печи для обжига; хранение готовой
продукции; кирпичи, уложенные крест-накрест; вымешивание
глины; кирпич пластического прессования; кирпич мокрого
прессования; кирпич сухого прессования.
Task 2. Match the terms (1–8) with the definitions (A–H).
1 – mining
3 – forming
5 – hacking
7 – preparing raw
materials
2 – firing
4 – drying
6 – cooling
8 – de-hacking
A: tempering for production of plastic, homogeneous clay
mass.
B: process of loading a kiln or kiln car with bricks.
C: evaporation of moisture in drying chambers.
D: process of heating bricks to a high temperature in order to
make them hard, durable, weather and water resistant.
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E: extraction of shales, surface or fire clays from open pits.
F: the process of unloading a kiln or kiln machine after bricks
have cooled.
G: breaking up large clay lumps and stones before mixing.
H: the process of gradual lowering the temperature inside the
product.
Task 3. Mark the statements as TRUE (T) or FALSE (F).
Correct the false statements.
1. Brick is a building material usually made as square blocks.
2. Brick is made of clay or shale.
3. Bricks are produced by mixing ground clay with water,
forming the clay into the desired shape, drying and firing.
4. Clay for brick manufacturing must have sufficient wet and
air-dried strength, plasticity.
5. There are three main kinds of clay used for brick
manufacture.
6. Brick laying is much more complicated process compared
to stone masonry.
7. The first brick-making machines were invented in the
middle of the 20th century.
8. Five general phases are involved into brick manufacturing
process.
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Text 3. Read the text.
TECHNOLOGY OF CONCRETE MANUFACTURE
Fig. 9. Manufacture of concrete
Concrete is the only material without which it is difficult to
imagine any construction. The uniqueness of this material allows it
to be used in the manufacture of foundations, walls, columns, various slabs, etc.
At present, the technology of mass production of the main
components of concrete allows it to compete with recognized natural materials such as stone or granite. Its basic strength and technological properties depend largely on how the concrete is prepared.
In general, this process is quite simple. It can be done by one's own
efforts and requires only a careful approach.
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Characteristics of concrete:
− strength;
− ductility;
− watertightness;
− rigidity;
− frost resistance;
− durability, etc.
Basic properties of concrete
Concrete is a mixture of cement mortar and various fillers and
additives. In turn, cement mortar (or the simplest concrete) consists
of a mixture of cement and sand, prepared as a water solution. The
full composition of a particular type of concrete is determined by
the formulation, depending on the purpose of the material.
The main parameter of concrete in determining its purpose
and quality is the mechanical compressive strength, i.e. the
resistance to vertical load. The strength mainly depends on the
strength properties of the cement (grade of cement used) and to
some extent on the content and quality of other components. To
increase the strength properties of special types of concrete,
reinforcing additives can be included in their composition.
The technological parameters of concrete can include
elasticity (plasticity), viscosity and homogeneity of the mortar.
Plasticizers and other additives can be added to the mixture in order
to facilitate the placement of the material and improve the
appearance of the product. Viscosity problems are solved by
changing the volume of water; and the homogeneity of the mass
depends on the quality of mixing.
An important property of concrete is that the final drying
process is very slow, during which the material increases strength.
It takes at least six months before the concrete is completely dry;
and it will reach its maximum strength after approximately
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12 months. This property of concrete is mainly determined by the
characteristic of the cement.
Cement, sand and aggregate
Cement
Cement is the base of concrete. It largely determines the
strength and monolithic nature of the entire compound. The most
common cement used in concrete is Portland cement, which is made
up of almost 80 % calcium silicate and has good adhesion to other
materials. Portland cement is usually made from limestone
produced by heating limestone and clay minerals in a kiln to form
clinker, grinding the clinker, and adding 2 to 3 % of gypsum.
Sand
Sand is one of the main components (filler) of concrete,
providing its volume and structure. In general, building sand is
a mixture of solid silicate particles sized 0.15–5 mm. Depending on
its origin, sand is divided into river sand, sea sand, lake sand, quarry
sand, gully sand, etc.
Aggregates
Crushed stone and gravel are used as bulk aggregates for
concrete. They are loose material in the form of rock pieces; and
they provide basic strength. The size of the pieces used for concrete
ranges from 5 to 35 mm.
Making concrete
Fundamentals of concrete and reinforced concrete
technology.
This technology involves the following basic operations:
preparation of the initial components (preparation of components
includes the removal of impurities, sifting and weighing according
to the prescription), preparation of components mixture, and mixing
the components with water.
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Properly prepared concrete is necessary for any construction
work: laying the foundation, pouring the floor, installation of
partitions, etc. The work is one of the most labor-intensive one.
The durability and reliability of the entire structure depends
on its quality.
Task 1. Match English and Russian equivalents.
1. Strength
a) железобетон
2. Rigidity
b) портландцемент
3. Portland Cement
c) заполнитель
4. Mortar
d) клинкер
5. Durability
e) примесь/добавка
6. Clinker
f) фундамент
7. Admixture
g) прочность
8. Aggregates
h) жесткость
9. Reinforced Concrete
i) раствор
10. Foundations
j) долговечность
Task 2. Mark the statements as TRUE (T) or FALSE (F).
Correct the false statements.
1. The uniqueness of concrete allows it to be used in the
manufacture of foundations, walls, columns, etc.
2. Cement mortar does not consist of a mixture of cement and
sand, prepared as an aqueous solution.
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3. The most common type of cement used all over the world
is Portland cement.
4. Portland cement is a fine powder, usually made from
limestone.
5. Concrete is produced by combining mineral aggregates,
a binder, chemical additives, and water.
6. Concrete made with natural cement is stronger and more
durable than concrete made Portland cement.
7. Clinker is a large rotary kiln used for cement burning.
8. The manufacturing process of concrete is simple enough.
Task 3. Translate the sentences into English.
1. Портландцемент – наиболее распространенный тип
цемента, широко используемый в качестве основного
ингредиента для бетона, строительного раствора, шту-
катурки.
2. Этот мелкий порошок получают путем нагревания из-
вестняка и глинистых минералов в печи и добавления
2–3 % гипса.
3. Бетон – это строительный материал, созданный путем
соединения минерального заполнителя (песка, гравия
или щебня), вяжущего материала, химических добавок
и воды.
4. Процесс изготовления бетона прост.
5. Бетон является идеальным материалом для строительства
дорог, мостов, систем водоснабжения и канализации, за-
водов, аэропортов, железных дорог и других сооружений.
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Text 4. Read the text.
REINFORCEMENT MANUFACTURING OPERATIONS
Fig. 10. Manufacture of reinforcement
The production of reinforcement is a rather complex process
including a sequence of several operations.
Preparation of reinforcement rods. Reinforcing steel, usu-
ally available in reels with a diameter of less than 10 mm is used
for the production of reinforcing rods. The process is carried out
with precision automatic cutting machines. The preparation of reinforcement rods from large-diameter steel, supplied in rods, is
carried out by joining them together on contact-welding machines,
followed by cutting on power-driven cutters. Automated assembly
lines are required for the technical cycle process. They are shifting
and clamping equipment, devices for measuring length and eject-
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ing of cut reinforcing rods. Special factory equipment is used for
curving bent parts of finished rods. Then, they are assembled into
frameworks.
Manufacture of reinforcement grids and frameworks. Pre-
made rods of electric-arc or contact (spot) welding are further used
for the production of reinforcement frameworks and grids. Singlecontact stationary machines are generally used for contact welding. For flat frameworks and broad reinforcement grids welding
multiple-spot automated lines are used. As it’s extremely im-
portant to ensure the proper quality of the welded reinforcement,
different methods of control are applied. They include the magneto-graphic method, illumination by gamma rays, and ultrasonic
“defectoscopy”.
Manufacture of reinforcement for prestressed reinforced-
concrete structural members. For the production of reinforcement
for prestressed reinforced concrete structures, special equipment is
used. These machines are designed for the operation of unrolling
the reinforcement, measuring the required length, cutting and assembling packages consisting of individual rods, several wires, or
strands. The stretching (tensioning) of the reinforcement is carried
out by hydraulic jacks. There is a technology of tensioning reinforcement by electro-thermal method. After the reinforcement is
placed into the form, it is lengthened by heating to a temperature of
300–450 °C. High voltage current, caused by heating is passed
through the reinforcement. The reinforcement in the heated state
with fixed ends is laid in the form. It is subjected to a predetermined
stress as a result of cooling. Such reinforced concrete products are
mainly used in residential construction.
Assembly and installation. Various types of welding are used
to produce three-dimensional or flat frames with individual rods.
Then, they are used for the construction of equipment foundations,
assembly and installation of reinforcement in monolithic concrete
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